1. Field of the Invention
The invention relates generally to the field of seismic data acquisition. More particularly, the invention relates to methods for processing seismic data to reduce the effects of noise.
2. Background Art
Seismic survey data are used to infer structure of the Earth's subsurface and to infer composition of the rock formations in the Earth's subsurface. Seismic survey data are acquired by deploying a seismic energy source at a selected position near the Earth's surface, and deploying one or more seismic receivers at selected positions near the Earth's surface in the vicinity of the seismic energy source. The source may be an explosive, an air or water gun, a vibrator, or arrays of such devices. The seismic energy source is actuated at various times, and a record is made with respect to time of signals detected by the one or more seismic receivers.
Seismic energy radiates generally downwardly from the source until it reaches one or more subsurface acoustic impedance boundaries in the subsurface. The seismic energy is reflected upwardly, back through the Earth formations, until it is detected by the one or more receivers near the Earth's surface. Seismic surveying is also conducted from the surface of bodies of water (marine seismic surveying), such as the ocean, by towing an air gun, water gun or arrays of such guns near the water surface behind a seismic survey vessel. Seismic receivers are towed by the same or a different vessel. Irrespective of whether the seismic survey data are recorded on land or on a body of water, the recordings of detected seismic energy are used to infer the structures of and the composition of the rocks in the Earth's subsurface. Typically, structures are inferred from the travel time of the reflected seismic energy from the source to the one or more receivers. Composition may be inferred from the seismic energy travel time, and characteristics of the detected seismic energy, such as its amplitude, phase and frequency content.
In order to accurately infer the subsurface structure and composition of the Earth's subsurface, seismic data recordings should be as free as is practical from the effects of noise. Noise may result from any one of a number of sources, including electronic noise in the various components of the data recording system, “burst” noise from an extraneous source including the seismic vessels in a marine survey and drilling and/or other industrial equipment in a land-based seismic survey. Many methods are known in the art for attenuating the effects of various types of noise present in seismic survey data. Some methods known in the art include attenuation of certain components of the seismic data recordings, such as components being outside of a selected frequency range, or having amplitude range or other characteristic of the seismic data falling outside a selected range or value, or above or below a selected threshold.
Methods known in the art, for example, K (trace mix), F–K (frequency-wavenumber), and Tau-p (slant stack) for processing seismic data to reduce the effect of noise are susceptible to trace-to-trace statics. What is needed is a robust method for reducing effects of noise in seismic data that has reduced susceptibility to trace-to-trace statics.